In the field of spark plugs, Japanese Patent No. 5662622 discloses a technique in which a tip is welded to an electrode based on Ni and containing Cr and Fe. According to the technique disclosed in Japanese Patent No. 5662622, an oxide film mainly formed by Cr ensures that the electrode has sufficient oxidation resistance. Fe alleviates the stress in the electrode due to the difference in thermal expansion coefficient between the tip and the electrode.
However, the above technique in the related art has the following problem. As the heat rating of the spark plug becomes higher, the center electrode undergoes a larger temperature change, and the oxide film peels off more easily due to the thermal expansion of the center electrode. As a result, the center electrode may corrode due to sulfur remaining in fuel and may thus wear quickly.
The present invention has been made to address the foregoing problem. An advantage of the present invention is a spark plug including a center electrode with improved wear resistance.